Outboard motor underwater exhaust valve



Oct. 9 5 J. c. BANDLl OUTBOARD MOTOR UNDERWATER EXHAUST VALVE FiledApril 18, 1949 Patented Oct. 9, 1951 OUTBOARD MoToR UNDERWATER EXHAUSTVALVE,

John C. Bandli, Minneapolis, Minn; assignor to Scott-AtwaterManufacturing Company, Minneapolis, Minn., a corporation of MinnesotaApplication April 18, 1949, Serial No. 88,117

This invention relates to an outboard motor and particularly to acontrol means or valving means for controlling the exhaust from saidmotor. When an outboard motor of the modern type is in operativeposition on a boat, the casing of said motor with an exhaust passageextending therethrough has a terminal portion disposed below the surfaceof the water and said passage has a discharge opening for the exhaustdisposed below the surface of the water. It has been the universalpractice to have this discharge passage open at its bottom. As a resultof the exhaust passage being open in the water at its lower end when themotor is at or very near a stopped condition, the water enters theexhaust passage and rises therein for a considerable distance. When themotor is running at certain speeds the exhaust gases must clear thiswater from the exhaust passage thus causing poor and unreliableperformance.

It has been the universal practice to have an auxiliary exhaust openingextending from the said exhaust passage and disposed above the surfaceof the water so that the exhaust gases can be discharged through thisauxiliary opening at idling or slow speeds. When the motor speed isincreased the exhaust gases will force the water out of the exhaustpassage in the casing, and discharge below the water surface. With theauxiliary exhaust passage above the water line, when the motor speed isincreased, a point is reached .at which the exhaust gases clear thewater from the exhaust passage and break through to the ;water surfacethrough and above the exhaust opening. This point is called the breakthru.

Unstable speed conditions exist at throttle settings where underwaterexhaust break thru occurs, resulting in erratic motor operation andcarburetor action in the conventional motor. As the break thru occurs,the engine will suddenly increase in speed. This occurrence at constantthrottle settings causes an' erroneous metering ofthe carburetor whichis practically impossible to correct by conventional means as nowprovided on motors.

Athigher speeds the impedance of the present structure to the dischargeof exhaust at the underwater outlet is no greater than the usualopposing ef'fect of water in-flow in the conventional open system of theprior art. Tests have shown that top revolutions per minute and positiveindications of power output are as great as or greater than attainedwith conventional systems heretofore used.

It is an object of thisinvention to. provide an 3 Claims. (Cl. 115-17)outboard motor having an exhaust passage, a discharge opening for saidpassage disposed below the surface of the water, together with means ator near the discharge opening which permits substantially only anoutward fiow of gases and liquids from said exhaust passage.

It is also an object of this invention to provide an outboard motorhaving an exhaust passage, said passage having a lower or terminalportion disposed below the surface of the water and having a dischargeopening in said terminal portion, together with means controlling saiddischarge opening and being movable by the exhaust gases.

It is a further object of the invention to provide an outboard motorcomprising one or more cylinders, a casing having an exhaust passageleading from said cylinder or cylinders and having a lower portiondisposed below the surface of the water and provided with a dischargeopening together with a valve at or adjacent said discharge opening andresiliently urged toward closed position so that the entry of water intothe casing and exhaust passage is substantially prevented, said motorpreferably having only the one exhaust discharge opening.

It is more specifically an object of the invention to provide anoutboard motor having one or more cylinders and having a casing with anexhaust passage extending therethrough, said casing having a lowerportion normally disposed below the surface of the water when said motoris in operative position on a boat, said portion having a dischargeopening together with a valve extending across said discharge openingand resiliently held in closed position when the motor is not running,which valve may take the form of a thin resilient plate secured at oneside of said casing.

These and other objects and advantages of the invention will be fullyset forth in the following description made in connection with theaccompanying drawings in which like reference characters refer tosimilar parts throughout the several views and in which:

Fig. l is a view in side elevation of an outboard motor;

Fig. 2 is a partial vertical section through said. motor showing acylinder and exhaust passage;

Fig. 3 is a partial vertical section similar to Fig. 2 and shown on anenlarged scale; and

Fig. 4 is a view in side elevation as seen from the right of Fig. 3.

Referrin to the drawings, an outboard motor is shown comprising a casing[0. A hood II is disposed above casing I0 having a lower portion 1 laanda top portion llb, which hood encloses th power head of the motor whichin turn comprises one or more cylinders I2 having the usual pistons l3therein, which pistons have the con necting rods [4. Cylinder I2 isshown as having a cap or head l2a thereon in which is disposed the usualspark plug [5. A steering lever I6 is shown, as is also a sparkadjusting lever 17. The casing I i! is pivoted to a bracket 19 adaptedto clamp the motor to a boat transom, which bracket has therein one ormore screw clamps 20 provided with operating handles .21.. The usualpropeller 21 of the outboard motor is also shown in Fig. 1. Casing Ithas an exhaust passage Illa extending vertically therethrou'gh which communicates with the cylinder or cylinders 12 through cylinder exhaustports i 21). Casing 1 11a has a lower terminal portion b in which isformed the exhaust discharge opening Itc. 'Portion lilb projectslaterally some distance and the casing in said portion in the embodimentof the invention illustrated, is streamlinedso that opening 10c and :asection of portion Nib parallel to the plane of said opening is ofcuspid shape. A valve 24 is provided, and whil the form and location ofthis valve could :be varied, in the embodiment of the inventionillustrated said 'valve comprises a thin resilient plate. Said plat issecured at its lower and straight edge portion to -a plate 25 whichextends across the bottom of casing Il 'fl. Plate 7.5., :together withth propeller "shaft housing 26, are secured to :casing .I t in anysuitable manner, by bieing'bolted thereto. Valve 2-4 can be secured toplate v25 in any suitable manner, :as by leeing welded, riveted, boltedor brazed thereto.

In operation theimotor will b operated .as usual and the exhaust gaseswilltpassfrom'the cylinder or cylinders [.2 through exhaust port :orlports 12b into the 'exhaustpassage 110a. The resiliency of valve 324.holds the same against :the end of casing Illaso thattheop'ening Hlciisclosedwhen the motor is inotirunning. This at :said time .retards theentry TOT water into the casin so that substantially no water now entersthe exhaust passage. When the motor is running .at .110 :speed or idlingthe valve :is substantially closed :sothat the exhaust passage isthuskept substantiallyclear of water andithe :water does snotriseappreciably in said :passage as is the common "occurrence when :theexhaust discharge :passage is openias .in the :prior art. The :exhaustpressure, in thenormalrangeiofpoperationtis of sufficient magnitude toopenvalve z l and permit the escape of the exhaust gases. Whenthezexnhaus't pressure is relieved, 'valve24 moves toward closed.position, At .all speeds therefore the exhaust passage is keptsubstantially :free of water.

The provision of valve .24 has madeiaaleryremarkable difference in theoperation .of the motor. Heretofore, as stated, when the :motor wasoperating at low speeds or :idling, water would rise in the exhaustpassage to ia considerable height. When the motor was :accelerated, theexhaust gases would haveto'forceithis water out of the exhaust passage.The back pressure arising from this :expulsionJo'f water icaused.sluggish operation of :the motor, LandgresuIted inerratio action andinstability or .speed and carburetor action, .particularly upon changing.sp'eed. Since the exhaust pressure at low and idling speeds Was notsufficient to expel-the WaterLin th'e =:exhaust :passage, an auxiliaryexhaust opening was provided well abovetthe water line; giving :rise toobjectionable noise at all times. With the exhaust opening is notnecessary. At the lower and idling speeds the motor runs with almostunbelievable quietness. This is an accomplishment never before known inan outboard motor. Formerly the exhaust through the auxiliary exhaustopening was quite noisy. The exhaust discharge now occurs a very regularand uni- .form manner .at .all speeds and the action of the motorcarburetor during the acceleration period has been vastly improved. Infact the provision of valve 24 has made possible much lower speeds thanwere heretofore attainable. The motor can now be operated with greatstability below 400 revolutions per minute.

The expansion chamber formed by the exhaust passage is appreciablyincreased in size by the elimination of practically all water. It isalso cooled by being "submerged through a considerable .portion of itsextent. Two-cycle motors with underwater exhaust systems operate more'efiiciently when the volume-of the chamber connecting the cylinder withthe underwater outlet is increased. Also a further increase in motorefiiciency results when the chamber is cooled, since the hot exhaustgases contract as they are cooled.

An outboard motor using the subject invention utilizes these benefits toa greater degree than heretofore possible. Unstable operation results ifthe expansion chamber erratically varies in size as in the conventionaloutboard motor heretofore known in the art, due to rise and fall of thewater level :in the open underwater exhaust passage. Such variation inthe volume of the exhaust passage arose from various causes, such apulsation of the exhaust pressure, wind and wave effects on boatattitude and changing of boat'trim as passengers change their positions,etc.

From the above description'it'willtbeseen that .I have provided meansfor greatly .improving the operation of an outboard motor. As abovestated, the exhaust passage is kept clear and the exhaust gases are notcompelled to move appreciable amounts rof -water from the exhaustpassage. The operation of the .motor has been immensely improved and'thenoise of operation at all but very highspeeds has been very greatlyreduced. The invention is simple and yet highly efficient and infact'constitutes a wonderful discovery and advance in the :art. The.structurehas'been amply demonstrated in actualipractice and found to bevery successful and .efficient.

It will of course 'be understood that various changesmay .be made in theform, details, arrangement and proportions of the parts, withoutdeparting from the scope of applicants invention, which generallystated, consists in ..-a device capable of carrying .out :the objectsabove setforth, in .thetparts .andrcombinations of parts disclosedanddefined in the appended claims.

"What :is claimed :is:

1. An outboard'motonstructurehaving in com- :bination, .a cylinder .fromwhich exhaust gases pass, a casing having an exhaust passageexitendingtherethrough connected to said cylinder, said casing.extending :downwardly and having a terminal discharge opening at itslower end disposed .well .belowthe surface of the water when .said motoris in operative position, a valve comprising aresilient sheet :securedto said casing 'iat oneiside offsaid opening and adapted'to close saidopening, said valve normally being held closed by its resiliency butadapted to-be opened zpresent construction usinguvalveadgthis auxiliarybyltheiexhausttdfi-saidlmotor,

2. In an outboard motor including a. powerhead at its upper portion, adriveshaft casing extending downwardly quite a distance from saidpowerhead, said exhaust casing formed to provide a passage for exhaustgases from said power head to the lower end of said exhaust casing, thelower end of said exhaust casing formed to provide a below water leveldischarge opening, and a resilient plate valve mounted over said openingand biased to close the latter thereby precluding entry of water intothe exhaust passage, said resilient valve opening only under the impulseof exhaust gases for discharging the latter. Y

3. The structure set forth in claim 2 wherein said plate valve comprisesa resilient sheet, said sheet being secured along its lower edge to anedge of said discharge opening, said sheet being 6 a normally held inclosed position by its resiliency but adapted over its upper portions touncover said opening under exhaust impulse.

JOHN C. BANDLI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

